Liquid filtration membranes for aqueous media may be in hollow fiber or flat sheet configurations and must be porous, hydrophilic, have excellent mechanical properties to support the membrane during manufacture and use and must have adequate thermal properties to prevent the membrane from degrading during high temperature processes. Furthermore, these membranes must have nonspecific protein binding, such that membrane fouling is minimized. Membrane fouling is a major concern, resulting in reduced efficiency due to flux decline, high cleaning and maintenance costs and low membrane lifetimes.
Typical membrane materials are hydrophobic and require an additive to make the membrane more hydrophilic. Polysulfones have the mechanical and thermal properties necessary for liquid filtration membranes, but these polymers are insufficiently hydrophilic. To improve their hydrophilicity, polysulfones have been blended with hydrophilic polymers, such as polyvinylpyrollidone (PVP). However, PVP is water-soluble and is slowly leached from the porous polymer matrix creating product variability.
Thus, hydrophilic porous membranes possessing excellent thermal, mechanical properties and improved fouling resistance are desired for longer service lifetimes.